The technology described herein relates to methods and arrangements in a Node B in a UMTS terrestrial radio access network (UTRAN). The UTRAN is illustrated in FIG. 1 and comprises at least one Radio Network System 100 connected to the Core Network (CN) 200. The CN is connectable to other networks such as the Internet, other mobile networks e.g. GSM systems and fixed telephony networks. The RNS 100 comprises at least one Radio Network Controller 110. Furthermore, the respective RNC 110 controls a plurality of Node-Bs 120,130 that are connected to the RNC by means of the Iub interface 140. Each Node B covers one or more cells and is arranged to serve the User Equipment (UE) 300 within said cell. Finally, the UE 300, also referred to as mobile terminal, is connected to one or more Node Bs over the Wideband Code Division Multiple Access (WCDMA) based radio interface 150.
In 3GPP Release 6, the WCDMA standard is extended with the Enhanced Uplink concept—the Enhanced Dedicated Transport Channel, E-DCH. A further description can be found in 3GPP TS 25.309 “FDD Enhanced Uplink; Overall description”. This concept introduces considerably higher peak data-rates in the WCDMA uplink. Features introduced with E-DCH include fast scheduling and fast hybrid ARQ with soft combining, both of these features are located in the Node B.
HARQ is a more advanced form of an ARQ retransmission scheme. In conventional ARQ schemes the receiver checks if a packet is received correctly. If it is not received correctly, the erroneous packet is discarded and a retransmission is requested. With HARQ the erroneous packet is not discarded. Instead the packet is kept and combined with a result of the retransmission. That implies that even if both the first transmission and the retransmission are erroneous, they may be combined to a correct packet. This means that fewer retransmissions are required.
Fast scheduling means that the Node B can indicate to each UE the rate the UE is allowed to transmit with. This can be done every TTI, i.e. fast. Thus, the network is able to control the interference in the system very well.
In HS-DSCH (High Speed Downlink Shared Channel), that is described in 3GPP TS 25.308 “UTRA High Speed DownLink Packet Access (HSDPA); Overall description; Stage 2, the scheduling is also located in the Node B. In HS-DSCH the scheduling is rather straight forward since the Node B scheduler has full knowledge of the data that needs to be transmitted in downlink. Based on the amount of data available for different UEs, the priority of the data and the radio channel quality which is indicated by the UE through the Channel Quality Indicator (CQI) measurements, the scheduler determines which data that should be transmitted to each UE.
On E-DCH the situation is different. The Node B scheduler has no direct information about the data that is to be transmitted from the UEs. Thus the UEs are required to indicate the amount of data available, the priority of the data, the transmitter power available etc. to the Node B through scheduling requests. When the Node B has received the scheduling request from the UE and has decided to schedule the UE based on the received scheduling requests, it transmits an absolute grant (AG), also denoted scheduling grant indicator herein, to the UE, indicating the amount of data or actually with which power the UE is allowed to transmit.
Before an uplink data burst can be transmitted, the UE must first transmit a scheduling request to the Node B, to inform the Node B that data is available for transmission. After a reception of the AG from the Node B the data burst can be transmitted. Thus, this procedure causes a delay in the beginning of a data transfer and potentially for each burst that is transmitted uplink, depending on how long the absolute grant is valid.
The delay caused by scheduling can partly be avoided by either using non-scheduled transmissions or issuing permanent absolute grants to all UEs. The non scheduled transmissions imply that the network configures a certain rate statistically that the UE is allowed to use instantaneously without sending a scheduling request. The drawback of this solution is that the configured rate must be rather high in order to support all possible traffic scenarios and may therefore require a large hardware allocation in the network and cause high interference. In the other solution, to permanently issue an absolute grant, it is possible to quickly change the value of the grant or remove the grant if the load of the network increases. However, this other solution has the drawback that the network does not know which users that really need the permanent grant and the risk is therefore that the performance of the uplink data transmission is impacted. Accordingly, it would be desired to avoid said delay and at the same time avoid the drawbacks mentioned above.
Many applications mainly involve downlink data transfer, e.g. file download, video streaming, and web surfing. The downlink scheduling only imposes a small delay unless the system load is very high. However, since most applications involve sending feedback messages in the uplink, such as Transfer Control Protocol (TCP) acknowledgements (ACK) and Radio Link Control (RLC) ACKs, the delay in uplink scheduling will affect the performance significantly of the downlink data traffic.